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Offline Eugene52Topic starter
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« Reply #260 on: March 24, 2010, 08:35:44 am »
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Quote:Posted by ameen
Hello

We have built one, but it does not work. I hear a voice when running and then press reboot and the sound disappears and the device is not sensitive to the metals.
Is the resistance side of 740 should be 1 watt.
ne 556 heat
And also a warm 740
Can you help me
Forgive me for my bad English


Please use the schematic I posted a few days ago . If you have less than 2.0 ohms on your search coil the IRF740 will get hot . You need to wind a new search coil try with at least 2.9 ohms dc
HH........Eugene

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Offline raff33
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« Reply #261 on: March 24, 2010, 10:12:02 am »
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hi Eugene,
 but the schematic you posted is for double side not for single side........ Undecided
Regards...........Raff33

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« Last Edit: December 31, 1969, 06:00:00 pm by raff33 »
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Offline Eugene52Topic starter
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« Reply #262 on: March 24, 2010, 10:49:55 am »
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Quote:Posted by raff33
hi Eugene,
 but the schematic you posted is for double side not for single side........ Undecided
Regards...........Raff33


You are correct , makes sense now !!!!  The single side PCB and double side PCB use different schematics but they are not too much different , just enough to give everyone a slight headache . I will go back and make sure that the right schematic goes to the right pcb board . The best , most accurate , most used schematic is the one I just posted above . And the single side PCB board is the easiest to make .  Shocked   Idea    The Delta Pulse Metal Detector project is the most built and most popular in the world !!!
HH............Eugene

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« Last Edit: December 31, 1969, 06:00:00 pm by Eugene52 »
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« Reply #263 on: March 24, 2010, 11:05:07 am »
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hi Eugene ,
now i inderstand ........  Idiot
what the resistance prefer for search coil 1m*1m .......please
 thanks for helping  Wink

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« Last Edit: December 31, 1969, 06:00:00 pm by raff33 »
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Offline Eugene52Topic starter
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« Reply #264 on: March 24, 2010, 11:21:55 am »
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Quote:Posted by raff33
hi Eugene ,
now i inderstand ........  Idiot
what the resistance prefer for search coil 1m*1m .......please
 thanks for helping  Wink


Remember sometimes on very large diameter search coils you may have to add a small value resistor in series with the coil to keep the total resistance above 2.5 ohms !!! I will look up the specs you need again for the 1 meter by 1 meter coil . I posted it already on this forum a few times plus I know I have alzheimers at 53 years old !!   Cheesy
HH........Eugene

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« Reply #265 on: March 24, 2010, 11:41:27 am »
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Hello Eugene,
I have finished too delta Pulse but im getting also poor detecting...i have used the single side PCB scheme all functions all things acording to your specs but still poor detecting..The Delta runs good but it seems to me instabil.The only thing instead LF357  i used  LF356 .Is that the problem?..
My coil is 40 Cm @ 23 Turns , 0,5 wire.
I have included a pic of my PCB...
Whats wrong?

Regards
Marius

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« Last Edit: December 31, 1969, 06:00:00 pm by steaua581 »
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Offline Eugene52Topic starter
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« Reply #266 on: March 24, 2010, 12:59:32 pm »
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Quote:Posted by steaua581
Hello Eugene,
I have finished too delta Pulse but im getting also poor detecting...i have used the single side PCB scheme all functions all things acording to your specs but still poor detecting..The Delta runs good but it seems to me instabil.The only thing instead LF357  i used  LF356 .Is that the problem?..
My coil is 40 Cm @ 23 Turns , 0,5 wire.
I have included a pic of my PCB...
Whats wrong?

Regards
Marius


LF357 and LF356 should have the same gain , only LF356 is a bit more noisy . You need to check signal at P4 [20k] potentiometer before jfet TLO62 opamp . You are loosing signal , there should be your problem . If you have an oscilloscope you can fix it very fast !!!!
HH.........Eugene

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Offline steaua581
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« Reply #267 on: March 24, 2010, 02:40:26 pm »
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Hello Eugene,
Thank you ...
I dont have an osciloscope...what would be the values i should look for and where exactly should i check i am using  with basic tools.
I am going to change LF356 w/ LF357....
Thanx Again

Regards
Marius

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« Reply #268 on: March 24, 2010, 03:30:26 pm »
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Hi Eugene,
it is ok now ,with R5 is 680 ohm 1 watt . And R6 is 1 k ohm , changed C30 10.000 uf by 4,700 uf  . Seach coil 28cm diameter ,31tr with 3,5 ohms dc resistance . my DP can detect in air 1 euro at 25cm and a canet PEPSI 250ml at 70 cm ;many thanks........ Cheesy
but why it is not stable , i can't find lf357 i replace with TL071, T1: IRF840 , do you think the probleme is 23,24,25,26  (5%)...............? many thanks again

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Offline Eugene52Topic starter
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« Reply #269 on: March 24, 2010, 05:06:05 pm »
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Quote:Posted by raff33
Hi Eugene,
it is ok now ,with R5 is 680 ohm 1 watt . And R6 is 1 k ohm , changed C30 10.000 uf by 4,700 uf  . Seach coil 28cm diameter ,31tr with 3,5 ohms dc resistance . my DP can detect in air 1 euro at 25cm and a canet PEPSI 250ml at 70 cm ;many thanks........ Cheesy
but why it is not stable , i can't find lf357 i replace with TL071, T1: IRF840 , do you think the probleme is 23,24,25,26  (5%)...............? many thanks again


If you do not use TL062 for D5 then change the resistance of R23 , R24 to a maximum of 10 k ohm . The 4.7 K ohms 1% were used for optimized gain when using a TL062 in the circuit . R25 and R26 should be kept at the same value [balance] to the 4066 switches . You sound like your making good progress.
HH.............Eugene

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